From: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com> mainline inclusion from mainline-v6.15-rc4 commit 5bb12b1837c0bf7ddc84e27812f1693a126fe27a category: feature bugzilla: https://atomgit.com/src-openeuler/kernel/issues/8862 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- There can be a case where there are contiguous extents on the adjacent leaf nodes of on-disk extent trees. So when someone tries to write to this contiguous range, ext4_map_blocks() call will split by returning 1 extent at a time if this is not already cached in extent_status tree cache (where if these extents when cached can get merged since they are contiguous). This is fine for a normal write however in case of atomic writes, it can't afford to break the write into two. Now this is also something that will only happen in the slow write case where we call ext4_map_blocks() for each of these extents spread across different leaf nodes. However, there is no guarantee that these extent status cache cannot be reclaimed before the last call to ext4_map_blocks() in ext4_map_blocks_atomic_write_slow(). Hence this patch adds support of EXT4_GET_BLOCKS_QUERY_LEAF_BLOCKS. This flag checks if the requested range can be fully found in extent status cache and return. If not, it looks up in on-disk extent tree via ext4_map_query_blocks(). If the found extent is the last entry in the leaf node, then it goes and queries the next lblk to see if there is an adjacent contiguous extent in the adjacent leaf node of the on-disk extent tree. Even though there can be a case where there are multiple adjacent extent entries spread across multiple leaf nodes. But we only read an adjacent leaf block i.e. in total of 2 extent entries spread across 2 leaf nodes. The reason for this is that we are mostly only going to support atomic writes with upto 64KB or maybe max upto 1MB of atomic write support. Acked-by: Darrick J. Wong <djwong@kernel.org> Co-developed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> Link: https://patch.msgid.link/6bb563e661f5fbd80e266a9e6ce6e29178f555f6.1747337952... Signed-off-by: Theodore Ts'o <tytso@mit.edu> Conflicts: fs/ext4/ext4.h fs/ext4/inode.c Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/ext4/ext4.h | 19 +++++++++- fs/ext4/extents.c | 12 +++++++ fs/ext4/inode.c | 89 +++++++++++++++++++++++++++++++++++++++++++---- 3 files changed, 112 insertions(+), 8 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 7b4f35fd996d..948459f512b8 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -252,9 +252,19 @@ struct ext4_allocation_request { #define EXT4_MAP_UNWRITTEN BIT(BH_Unwritten) #define EXT4_MAP_BOUNDARY BIT(BH_Boundary) #define EXT4_MAP_DELAYED BIT(BH_Delay) +/* + * This is for use in ext4_map_query_blocks() for a special case where we can + * have a physically and logically contiguous blocks split across two leaf + * nodes instead of a single extent. This is required in case of atomic writes + * to know whether the returned extent is last in leaf. If yes, then lookup for + * next in leaf block in ext4_map_query_blocks_next_in_leaf(). + * - This is never going to be added to any buffer head state. + * - We use the next available bit after BH_BITMAP_UPTODATE. + */ +#define EXT4_MAP_QUERY_LAST_IN_LEAF BIT(BH_BITMAP_UPTODATE + 1) #define EXT4_MAP_FLAGS (EXT4_MAP_NEW | EXT4_MAP_MAPPED |\ EXT4_MAP_UNWRITTEN | EXT4_MAP_BOUNDARY |\ - EXT4_MAP_DELAYED) + EXT4_MAP_DELAYED | EXT4_MAP_QUERY_LAST_IN_LEAF) struct ext4_map_blocks { ext4_fsblk_t m_pblk; @@ -718,6 +728,13 @@ enum { /* Caller is in the atomic contex, find extent if it has been cached */ #define EXT4_GET_BLOCKS_CACHED_NOWAIT 0x0800 +/* + * Atomic write caller needs this to query in the slow path of mixed mapping + * case, when a contiguous extent can be split across two adjacent leaf nodes. + * Look EXT4_MAP_QUERY_LAST_IN_LEAF. + */ +#define EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF 0x1000 + /* * The bit position of these flags must not overlap with any of the * EXT4_GET_BLOCKS_*. They are used by ext4_find_extent(), diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 0797ccbf3c4e..c603ac90977c 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4491,6 +4491,18 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, allocated = map->m_len; ext4_ext_show_leaf(inode, path); out: + /* + * We never use EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF with CREATE flag. + * So we know that the depth used here is correct, since there was no + * block allocation done if EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF is set. + * If tomorrow we start using this QUERY flag with CREATE, then we will + * need to re-calculate the depth as it might have changed due to block + * allocation. + */ + if (flags & EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF) + if (!err && ex && (ex == EXT_LAST_EXTENT(path[depth].p_hdr))) + map->m_flags |= EXT4_MAP_QUERY_LAST_IN_LEAF; + ext4_free_ext_path(path); trace_ext4_ext_map_blocks_exit(inode, flags, map, diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 12f405aea850..1a7d31095b85 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -455,14 +455,71 @@ static void ext4_map_blocks_es_recheck(handle_t *handle, } #endif /* ES_AGGRESSIVE_TEST */ +static int ext4_map_query_blocks_next_in_leaf(handle_t *handle, + struct inode *inode, struct ext4_map_blocks *map, + unsigned int orig_mlen) +{ + struct ext4_map_blocks map2; + unsigned int status, status2; + int retval; + + status = map->m_flags & EXT4_MAP_UNWRITTEN ? + EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN; + + WARN_ON_ONCE(!(map->m_flags & EXT4_MAP_QUERY_LAST_IN_LEAF)); + WARN_ON_ONCE(orig_mlen <= map->m_len); + + /* Prepare map2 for lookup in next leaf block */ + map2.m_lblk = map->m_lblk + map->m_len; + map2.m_len = orig_mlen - map->m_len; + map2.m_flags = 0; + retval = ext4_ext_map_blocks(handle, inode, &map2, 0); + + if (retval <= 0) { + ext4_es_insert_extent(inode, map->m_lblk, map->m_len, + map->m_pblk, status); + return map->m_len; + } + + if (unlikely(retval != map2.m_len)) { + ext4_warning(inode->i_sb, + "ES len assertion failed for inode " + "%lu: retval %d != map->m_len %d", + inode->i_ino, retval, map2.m_len); + WARN_ON(1); + } + + status2 = map2.m_flags & EXT4_MAP_UNWRITTEN ? + EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN; + + /* + * If map2 is contiguous with map, then let's insert it as a single + * extent in es cache and return the combined length of both the maps. + */ + if (map->m_pblk + map->m_len == map2.m_pblk && + status == status2) { + ext4_es_insert_extent(inode, map->m_lblk, + map->m_len + map2.m_len, map->m_pblk, + status); + map->m_len += map2.m_len; + } else { + ext4_es_insert_extent(inode, map->m_lblk, map->m_len, + map->m_pblk, status); + } + + return map->m_len; +} + static int ext4_map_query_blocks(handle_t *handle, struct inode *inode, struct ext4_map_blocks *map) { unsigned int status; int retval; + unsigned int orig_mlen = map->m_len; if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) - retval = ext4_ext_map_blocks(handle, inode, map, 0); + retval = ext4_ext_map_blocks(handle, inode, map, + EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF); else retval = ext4_ind_map_blocks(handle, inode, map, 0); @@ -477,11 +534,23 @@ static int ext4_map_query_blocks(handle_t *handle, struct inode *inode, WARN_ON(1); } - status = map->m_flags & EXT4_MAP_UNWRITTEN ? - EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN; - ext4_es_insert_extent(inode, map->m_lblk, map->m_len, - map->m_pblk, status); - return retval; + /* + * No need to query next in leaf: + * - if returned extent is not last in leaf or + * - if the last in leaf is the full requested range + */ + if (!(map->m_flags & EXT4_MAP_QUERY_LAST_IN_LEAF) || + ((map->m_flags & EXT4_MAP_QUERY_LAST_IN_LEAF) && + (map->m_len == orig_mlen))) { + status = map->m_flags & EXT4_MAP_UNWRITTEN ? + EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN; + ext4_es_insert_extent(inode, map->m_lblk, map->m_len, + map->m_pblk, status); + return retval; + } + + return ext4_map_query_blocks_next_in_leaf(handle, inode, map, + orig_mlen); } static int ext4_map_create_blocks(handle_t *handle, struct inode *inode, @@ -592,6 +661,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, struct extent_status es; int retval; int ret = 0; + unsigned int orig_mlen = map->m_len; #ifdef ES_AGGRESSIVE_TEST struct ext4_map_blocks orig_map; @@ -643,7 +713,12 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, ext4_map_blocks_es_recheck(handle, inode, map, &orig_map, flags); #endif - goto found; + if (!(flags & EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF) || + orig_mlen == map->m_len) + goto found; + + if (flags & EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF) + map->m_len = orig_mlen; } /* * In the query cache no-wait mode, nothing we can do more if we -- 2.52.0